<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
<head>
	<meta http-equiv="Content-Type" content="text/html;charset=UTF-8">
	<title>Document</title>
	<script>
		window.onload=function(){
			document.getElementById("form1").onsubmit=function(){
				var unameVal = document.getElementById("uname").value;
				if(/^[a-z]\w{5,19}$/i.test(unameVal)){
					return true;
				}else{
					alert("用户名非法");
					return false;
				}
				
			}
		}
	</script>
</head>
<body>
	<form id="form1" method="post" action="2.php">
		用户名:<input type="text" name="uname" id="uname"/><br/>
		<input type="submit"/>
	</form>

</body>
</html>